[asterisk-dev] 'IAX2 call variable passing between servers '

[Tilghman Lesher]

On Thursday 27 July 2006 14:00, John Todd wrote:
> At 12:48 PM -0500 7/27/06, Tilghman Lesher wrote:
> >On Thursday 27 July 2006 11:55, Douglas Garstang wrote:
> >>  Found this thread on this list, from almost three years ago.
> >>
> >  > http://lists.digium.com/pipermail/asterisk-dev/2003-December/002
> >  >398.html
> >>
> >>  It talks about passing variables in IAX2.
> >>
> >>  Was any of it ever implemented?
> >
> >No, and it probably won't be, until it gets past the "wouldn't it be
> >cool if..." stage.  Not to mention that debugging a session where
> >the variables could change midexecution in the dialplan would be
> >pure hell.
>
> Can you explain a bit more how the variables might change
> mid-execution?  I don't quite follow this, but I perhaps had some
> assumptions that were built into my original idea that I did not make
> obvious.  Let me put a few of them out here for discussion:
>
>   - any variables with "outbound." as a prefix would be sent with
>       any Dial execution, and could not be altered once the Dial
>       has been run.  In other words: variables would be transmitted
>       only once to the remote server, during the call setup and could
>       and should not change during the call (though that does sound
>       like it could be done with both SIP and IAX2, it seems too
>       complex to tackle for a first swing at such variable
> transport.)

For such a restriction, there are less issues, but with such a
restriction, you'll also lose quite a bit of what people would like to
be able to do.  Additionally, there's no advantage to this system over
simply encoding your variables directly into the Dial string.

>    - any received variables would not change once the dialplan
> started executing on the receiving machine, so variables would not
> change once the call setup request had been accepted by the remote
> machine.  In other words, "inbound." prefixed variables would never
> change during the life of a call.
>
> The good news is that since I wrote that original post several years
> ago, there is now the ability to parse SIP headers within the
> dialplan, so that with a little creative string manipulation it is
> possible to move variables between two systems with SIP headers.  Now
> the only thing remaining is the ability to do the same thing with
> IAX2.  This seems a bit backwards - Asterisk seems like it should
> easily move variables around in it's native protocol instead of in
> SIP, but that's the way it is until someone comes up with the code.

I suppose you could hack in variables into the SIP headers, but that's
not really what that interface is for.

-- 
Tilghman